This invention relates to a process for polymerizing poly-2-alkyl-2-oxazoline (hereinafter poly-oxazoline) in an ethylbenzene diluent.
Typically, in the polymerization of poly-oxazolines as with other polymers, it is generally desirable to employ a solvent or diluent to prevent total polymerization of the ingredients and thus plug the polymerization train. As it is necessary to be able to transport the polymer between reactors and storage tanks, usually by pipes, a solvent or diluent is included to maintain a sufficient viscosity of the polymer to facilitate flow. Another consideration is that the diluent or solvent be easily extracted from the polymer once processing is complete.
Generally, the solvent or diluent is chosen such that it is compatible with the polymer to prevent phase separation. Thus, aromatic-type solvents or diluents are chosen for aromatic-type polymers and alkenyl-type solvents or diluents are chosen for alkenyl-type polymers.
Ethyl acetate has long been the solvent of choice for the polymerization of 2-alkyl-2-oxazoline monomer into poly-2-alkyl-2-oxazoline. Unfortunately, ethyl acetate was too volatile to be smoothly removed from the polymer, especially when utilizing polymerization equipment designed for polymerizing styrene. Chlorobenzene has suitable volatility but has unacceptable corrosive properties and is an aromatic-type solvent whereas poly-2-alkyl-2-oxazolines are not aromatic-type polymers.